1. Field of the Invention
This invention relates in general to earth boring drill bits and in particular to improved means for their lubrication.
2. Description of the Prior Art
Earth boring drill bits commonly utilize bearing lubrication systems. The successful lubrication of drill bit bearings depends upon an effective seal such as that disclosed in U.S. Pat. No. 3,397,928 issued to Edward M. Galle. The lubrication system typically includes a compensator that equalizes the pressure differential across the seal, as described in U.S. Pat. Nos. 3,007,750 and 3,137,508 to Cunningham. Further, it is advantageous to include a pressure relief valve to limit the internal lubrication system pressure to a selected magnitude above the pressure in the well bore, as disclosed in U.S. Pat. No. 3,476,195 issued to Edward M. Galle.
Problems arise from the complexity of the lubrication system, which normally includes a seal, a flexible membrane compensator and a pressure relief valve. Should there be a malfunction of any component, the effectiveness of the lubrication system will be destroyed. Shortly thereafter, a bearing failure is experienced. A reduction in the number of components in the system is therefore advantageous.